1. Field of the Invention
The present invention relates to a structure of a flying type magnetic head slider used in a magnetic disk drive.
2. Description of the Related Art
In recent years, a reduction in size and an increase in capacity of a magnetic disk drive as a kind of external storage device for a computer have been desired. One method of increasing the capacity of the magnetic disk drive is to increase the number of magnetic disks mounted on a spindle, and in association therewith the spacing between the magnetic disks in a recent magnetic disk drive has increasingly been reduced. In a recent magnetic disk drive, a flying type magnetic head adopting a contact start and stop (CSS) system has frequently been used. In such a flying type magnetic head adopting the CSS system, a magnetic head comes into contact with a magnetic disk when the disk drive stops operation, whereas the magnetic head is kept flying at a microscopic height from the disk surface by an air flow generating over the disk surface rotating at a high speed in recording or reproducing information.
In the flying type magnetic head adopting the CSS system, an electromagnetic transducer (magnetic head element) is built in a slider for receiving the air flow generating over the disk surface, and the slider is supported by a suspension. Accordingly, when the magnetic disk remains still, the slider including the electromagnetic transducer is in contact with the disk surface, whereas when the magnetic disk is rotated, a disk opposing surface of the slider opposed to the magnetic disk receives an air flow generated by rotation of the magnetic disk, and the slider flies from the disk surface. The electromagnetic transducer built in the slider is moved over the disk surface as being supported by the suspension to perform recording or reproduction of information at a given track.
In a magnetic disk drive employing a conventional flying type magnetic head slider, a pair of rails are provided on opposite side portions of a disk opposing surface of the magnetic head slider opposed to the disk surface. Each rail has a flat air bearing surface. Further, a tapering surface is formed on each rail so as to meet an air inlet end surface of the slider. The air bearing surface of each rail receives an air flow generated by high-speed rotation of a magnetic disk to fly the slider and stably maintains a microscopic distance between the disk surface and the electromagnetic transducer.
According to the CSS system, a high flying stability and a microscopic flying height (submicrons) can be ensured. However, when the disk remains still, rail surfaces (air bearing surfaces) of the slider are in contact with the disk. Accordingly, when the magnetic disk drive starts or stops operation, the air bearing surfaces relatively slide on the disk. To cope with such sliding, a protective film made of a hard material such as carbon and a lubricating layer for reducing friction and wear of the protective film to improve durability of the magnetic disk are formed on a recording layer of the disk. Owing to the presence of the lubricating layer, friction and wear of the protective film can be reduced. However, when the disk drive stops operation, there is a possibility that stiction between the disk and the slider may occur causing a problem that the disk drive cannot be restarted.
In association with a recent increase in the amount of information, the developments in high density, large capacity, and small size of a magnetic disk drive have become remarkable, and the occurrence of stiction has been greatly highlighted as a cause of faulty operation due to a reduction in torque of a spindle motor in association with the size reduction and due to the smoothing of the disk surface for the high density. To reduce the stiction between the slider and the disk, it has been proposed to perform crowning of the flying surfaces (rail surfaces) of the slider over the entire length in the longitudinal direction to thereby reduce a contact area between the slider and the disk.
While the slider thus crowned is effective for prevention of the stiction, there is a problem that variations in working accuracy are large and an increase in cost of the slider results, so that such a slider is unsuitable for mass production. Further, crowning is performed in the longitudinal direction of each flying surface of the slider, so that each rail surface of the slider becomes nearer to the disk than the electromagnetic transducer (head element) formed on an air inlet end surface of the slider, causing a problem that a spacing loss is produced.
Further, the use of a contact type head intended to attain a zero flying height has recently started to be considered in response to the development in high density, and it is therefore more important to prevent the stiction between the disk and the slider causing faulty operation and fracture of the electromagnetic transducer or the recording layer of the disk. To prevent this stiction problem, it has been proposed to provide a plurality of projections on the flying surfaces (air bearing surfaces) of the slider, thereby reducing a contact area between the slider and the disk surface (Japanese Patent Laid-open No. 8-69674).
A structure of a magnetic head slider 2 described in the above-mentioned publication will now be described in brief with reference to FIG. 1A. A pair of rails 4 and 6 are formed at opposite side portions of the magnetic head slider 2. The rails 4 and 6 respectively have flat air bearing surfaces 4a and 6a for generating a flying force during rotation of a magnetic disk. Further, tapering surfaces 4b and 6b are formed at air inlet end portions of the rails 4 and 6, respectively. A plurality of projections 10 are formed on the air bearing surfaces 4a and 6a of the rails 4 and 6. An electromagnetic transducer 8 is integrally formed on an air outlet end surface of the slider 2 at a position where the rail 4 is formed.
The magnetic head slider described in the above-mentioned publication is characterized in that the projections 10 are provided in order to avoid the contact between the air bearing surfaces 4a and 6a and the disk surface. With this structure, if a slight amount of dust is present on the disk surface in an actual disk drive, the dust tends to gather on the air bearing surfaces 4a and 6a at positions just downstream of the projections 10.
More specifically, in the magnetic head slider described in the above-mentioned publication, the rear ends of the projections 10 are present on the air bearing surfaces 4a and 6a. Accordingly, as shown in FIG. 1B, air flows near each projection 10 so as to pass over each projection 10 as shown by arrows A. At this time, a vacuum is generated near a position P at the rear end of each projection 10, and the air flow stays near this position P. As a result, the dust suspended in the air flow gathers near the position P, and in some case the dust is deposited at this position. Thus, in contrast with a slider without any projections, the conventional slider shown has a problem that the slight amount of dust has an adverse effect on flying characteristics of the slider.
The magnetic head slider described in the above-mentioned publication also has the following problem. As shown in FIG. 2A, the magnetic head slider 2 in an inoperative condition of the magnetic disk drive remains still in such a manner that the projections 10 are in contact with the surface of a magnetic disk 5. Reference numeral 7 denotes a fulcrum at which the slider 2 is supported by a suspension (not shown). When a starting rotational force having a direction of an arrow R is applied to the slider 2, the position of the slider 2 changes to a tilt position as shown in FIG. 2B because of the balance of moments about the fulcrum 7 of the slider 2. That is, the tapering surfaces 4b and 6b formed on the upstream side (air inlet side) of the air bearing surfaces 4a and 6a come into contact with the disk 5, causing stiction between the slider 2 and the disk 5.
The stiction force in this case is sufficiently smaller than that in the case that the slider has no projections and the entirety of the air bearing surfaces comes into contact with the disk. Accordingly, stiction trouble hardly occurs in the disk drive in general. However, a large force acts between the contact surfaces of the magnetic head slider and the magnetic disk, causing wear of the disk surface. As a result, wear powder generated at this time will subsequently behave as dust.